Numerics Configuration#
The algorithms used in DAMASK can be configured via a YAML file.
This optional file needs to be specified with the --numerics option when using the DAMASK grid or mesh solvers, or located in the current working directory and named numerics.yaml to be included in a simulation with MSC Marc.
Using damask.YAML is the recommended way for the generation and modification of numerics.yaml.
Hand-written files should be checked for correctness, e.g. with yamllint or on www.yamllint.com.
Reference Examples#
All available parameters are usually listed in the file examples/config/numerics.yaml.
The content of this file is shown below.
numerics#
# Default values of all available numerical parameters
# Please note that keys are case sensitive
solver:
grid:
N_staggered_iter_max: 10 # max number of field-level staggered iterations
N_cutback_max: 3 # maximum cutback level (0: 1, 1: 0.5, 2: 0.25, etc)
damage:
N_iter_max: 100 # maximum iteration number
eps_abs_phi: 1.0e-2 # absolute tolerance for damage evolution
eps_rel_phi: 1.0e-6 # relative tolerance for damage evolution
phi_min: 1.0e-6 # residual integrity
thermal:
N_iter_max: 100 # maximum iteration number
eps_abs_T: 1.0e-2 # absolute tolerance for thermal equilibrium
eps_rel_T: 1.0e-6 # relative tolerance for thermal equilibrium
mechanical:
N_iter_min: 1 # minimum iteration number
N_iter_max: 100 # maximum iteration number
eps_abs_div(P): 1.0e-4 # absolute tolerance for fulfillment of stress equilibrium
eps_rel_div(P): 5.0e-4 # relative tolerance for fulfillment of stress equilibrium
eps_abs_P: 1.0e3 # absolute tolerance for fulfillment of stress BC
eps_rel_P: 1.0e-3 # relative tolerance for fulfillment of stress BC
eps_abs_curl(F): 1.0e-10 # absolute tolerance for fulfillment of strain compatibility
eps_rel_curl(F): 5.0e-4 # relative tolerance for fulfillment of strain compatibility
alpha: 1.0 # polarization scheme parameter 0.0 < alpha < 2.0 (1.0: AL scheme, 2.0: accelerated scheme)
beta: 1.0 # polarization scheme parameter 0.0 < beta < 2.0 (1.0: AL scheme, 2.0: accelerated scheme)
update_gamma: false # update Gamma-operator with current dPdF (not possible if FFT: memory_efficient == true)
PETSc_options: -snes_type ngmres -snes_ngmres_anderson # PETSc solver options
FFT:
memory_efficient: true # precalculate Gamma-operator (81 doubles per point)
divergence_correction: size+grid # use size-independent divergence criterion {none, size, size+grid}
derivative: continuous # approximation used for derivatives in Fourier space {continuous, central_difference, FWBW_difference}
FFTW_plan_mode: FFTW_MEASURE # planning-rigor flags, see manual at https://www.fftw.org/fftw3_doc/Planner-Flags.html
FFTW_timelimit: -1.0 # time limit of plan creation for FFTW, see manual on www.fftw.org. (-1.0: disable time limit)
mesh:
N_cutback_max: 3 # maximum cut back level (0: 1, 1: 0.5, 2: 0.25, etc)
N_staggered_iter_max: 10 # max number of field level staggered iterations
p_s: 2 # order of displacement shape functions
p_i: 2 # order of quadrature rule required
bbarstabilization: false
mechanical:
N_iter_max: 250 # Maximum iteration number
eps_abs_div(P): 1.0e-10 # absolute tolerance for mechanical equilibrium
eps_rel_div(P): 1.0e-4 # relative tolerance for mechanical equilibrium
Marc:
unit_length: 1.0 # physical length of one computational length unit
homogenization:
mechanical:
RGC:
eps_abs_P: 1.0e+4 # absolute tolerance of RGC residuum (in Pa)
eps_rel_P: 1.0e-3 # relative ...
eps_abs_max: 1.0e+10 # absolute upper-limit of RGC residuum (in Pa)
eps_rel_max: 1.0e+2 # relative ...
Delta_a: 1.0e-7 # perturbation for computing penalty tangent
relevant_mismatch: 1.0e-5 # minimum threshold of mismatch
viscosity_exponent: 1.0e+0 # power (sensitivity rate) of numerical viscosity in RGC scheme
viscosity_modulus: 0.0e+0 # stress modulus of RGC numerical viscosity (0: without numerical viscosity)
# suggestion: larger than the aTol_RGC but still far below the expected flow stress of material
dot_a_ref: 1.0e-3 # reference rate of relaxation (about the same magnitude as straining rate, possibly a bit higher)
dot_a_max: 1.0e+0 # threshold of maximum relaxation vector increment (if exceed this then cutback)
Delta_V_max: 1.0e-5 # maximum allowable relative volume discrepancy
Delta_V_modulus: 1.0e+12
Delta_V_exponent: 5.0
phase:
mechanical:
r_cutback_min: 1.0e-3 # minimum (relative) size of step allowed during cutback in phase state calculation
r_cutback: 0.25 # factor to decrease size of step when cutback introduced in phase state calculation (value between 0 and 1)
r_increase: 1.5 # factor to increase size of next step when previous step converged in phase state calculation
eps_rel_state: 1.0e-6 # relative tolerance in phase state loop (abs tol provided by constitutive law)
N_iter_state_max: 10 # state loop limit
plastic:
r_linesearch_Lp: 0.5 # factor to decrease the step if Lp calculation fails to converge
eps_rel_Lp: 1.0e-6 # relative tolerance in Lp residuum
eps_abs_Lp: 1.0e-8 # absolute tolerance in Lp residuum
N_iter_Lp_max: 40 # stress loop limit for Lp
f_update_jacobi_Lp: 1 # frequency of Jacobian update of residuum in Lp
integrator_state: FPI # integration method (FPI = Fixed Point Iteration, Euler = Euler, Euler_adaptive = Adaptive Euler, RK4 = classical 4th order Runge-Kutta, RKCK45 = 5th order Runge-Kutta Cash-Karp)
eigen:
r_linesearch_Li: 0.5 # factor to decrease the step if Li calculation fails to converge
eps_rel_Li: 1.0e-6 # relative tolerance in Li residuum
eps_abs_Li: 1.0e-8 # absolute tolerance in Li residuum
N_iter_Li_max: 40 # stress loop limit for Li
f_update_jacobi_Li: 1 # frequency of updating the Jacobian of residuum in Li
generic:
random_seed: 0 # fixed seeding for pseudo-random number generator (0: use random seed)
Note
The YAML parser used in DAMASK does not support advanced features, such as references and line continuation statements, unless DAMASK was compiled with libfyaml.